Plasma monitor. Plasma or LCD which is better? Plasma screen working principle

On this page we will talk about topics such as: Information output devices, , Plasma monitors, Monitors with a cathode ray tube.

Monitor (display) a device for visual display of information, designed to screen output text and graphic information.

Characterized monitor diagonal size, resolution, grain size, maximum frame rate, connection type.

Monitor types:

• Colored and monochrome.
• Various sizes (from 14 inches).
• with different grains.
• Liquid crystal and cathode ray tube.

Monitor works under the control of a special hardware device - a video adapter (video controller, video card), which provides for two possible modes - text and graphics.

In text mode screen is broken (most often) into 25 lines with 80 positions in each line (2000 positions in total). Any character of the code table can be displayed in each position (familiarity) - an uppercase or lowercase letter of the Latin or Russian alphabet, a service sign (“+”, “-”, “.”, etc.), a pseudographic symbol, as well as a graphic image almost every control character. For each familiarity on the screen, the program working with the screen tells the video controller only two bytes - a byte with a character code and a byte with a character color and background color code. And the video controller generates an image on screen.

In graphics mode, the image is formed in the same way as on screen TV, - a mosaic, a collection of dots, each of which is painted in one color or another. On screen in graphics mode, you can display texts, graphics, pictures, etc. And when displaying tests, you can use different fonts, any sizes, fonts, any sizes, colors, letter arrangement. In graphics mode screen monitor is essentially a raster consisting of pixels.

Note

The smallest image element on the screen (dot) is called a pixel - from the English "picture element" ...

The number of horizontal and vertical dots that monitor capable of reproducing clearly and distinctly is called the monitor's dilution capability. The expression "dissolving power monitor 1024×768" means that monitor can output 1024 horizontal lines with 768 dots per line.

There are two main types monitor: liquid crystal and with cathode ray tube. Less common are plasma monitors And touch screen monitors.

monitors with a cathode ray tube.

Screen image cathode ray tube monitor is created by a beam of electrons emitted by an electron gun and the principle of their operation is similar to that of a TV set. This beam (electron beam) is accelerated by a high electrical voltage and falls on the inner surface of the screen, covered with a phosphor composition that glows under its interaction.

The phosphor is applied in the form of sets of dots of three primary colors - red (Red), green (Green) and blue (Blue). These colors are called primary, because their combinations (in various proportions) can represent any color of the spectrum. The color model in which the image on the monitor screen is built is called RGB. Sets of phosphor dots are arranged in triangular triads. The triad forms a pixel - a point from which an image is formed.

The distance between pixel centers is called dot pitch. monitor. This distance significantly affects the clarity of the image. The smaller the pitch, the higher the clarity. Usually in color monitors the pitch (diagonally) is 0.27-0.28 mm. With such a step, the human eye perceives the points of the triad as one point of a “complex” color.

On the opposite side tubes there are three (according to the number of primary colors) electron guns. All three guns are "aimed" at the same pixel, but each of them emits a stream of electrons towards its "own" point of the phosphor.

In order for the electrons to freely reach the screen, air is pumped out of the tube, and a high electrical voltage is created between the guns and the screen, which accelerates the electrons.

A mask is placed in front of the screen in the path of the electrons - a thin metal plate with a large number of holes located opposite the points of the phosphor. The mask ensures that electron beams hit only the dots of the phosphor of the corresponding color. The magnitude of the electronic current of the guns and, consequently, the brightness of the glow of the pixels, is controlled by a signal coming from the video adapter.

A deflecting system is put on the part of the flask where the electron guns are located. monitor, which causes the electron beam to run through all the pixels line by line from the top to the bottom, then return to the beginning of the top line, etc. The number of displayed lines per second is called the line refresh rate. And the frequency with which the image frames change is called the refresh rate.

Note

The latter should not be lower than 60 Hz, otherwise the image will flicker ...

LCD monitors.

LCD monitors (LCD) have less weight, geometric volume, consume two orders of magnitude less energy, do not emit electromagnetic waves that affect human health, but are more expensive than monitors with cathode ray tube.

liquid crystals- this is a special state of some organic substances, in which they have fluidity and the ability to form spatial structures similar to crystalline.

liquid crystals can change their structure and light-optical properties under the influence of electric voltage. By changing the orientation of crystal groups with the help of an electric field and using the liquid crystal a solution of a substance capable of emitting light under the influence of an electric field, it is possible to create high-quality images that reproduce more than 15 million color shades.

Majority LCD monitors uses a thin film liquid crystals placed between two glass plates. The charges are transmitted through the so-called passive matrix - a grid of invisible threads, horizontal and vertical, creating an image point at the intersection of the threads (somewhat blurry due to the fact that the charges penetrate into neighboring areas of the liquid).

plasma monitors.

Job plasma monitors very similar to the work of neon lamps, which are made in the form of a tube filled with low pressure inert gas. A pair of electrodes is placed inside the tube, between which an electric discharge is ignited and a glow occurs. Plasma screens are created by filling the space between two glass surfaces with an inert gas such as argon or neon.

Then, small transparent electrodes are placed on the glass surface, to which high-frequency voltages are applied. Under the action of this voltage, an electric discharge occurs in the gas region adjacent to the electrode. The gas discharge plasma emits light in the ultraviolet range, which causes the phosphor particles to glow in the range visible to humans. In fact, every pixel on the screen works like a regular fluorescent lamp.

High brightness, contrast and no jitter are the big advantages of such monitors. In addition, the angle relative to that at which a normal image can be seen on plasma monitors– 160° compared to 145° as in the case of LCD monitors. great dignity plasma monitors is their service life. The average life without changing the image quality is 30,000 hours. This is three times more than normal cathode-ray tube. The only thing that limits their wide distribution is the cost.

Monitor type - touch screen. Here, communication with the computer is carried out by touching a certain place with a finger on a sensitive screen. This selects the required mode from the menu shown on the screen. monitor.

Plasma Display Panel (PDP)

Only fifteen or twenty years ago, science fiction writers unanimously predicted the appearance of huge and completely flat television screens in the future. And now the fairy tale has finally come true, and anyone can buy such a screen.

The device of plasma panels

The principle of operation of the plasma panel is based on the glow of special phosphors when exposed to ultraviolet radiation. In turn, this radiation arises during an electric discharge in a highly rarefied gas medium. With such a discharge, a conductive “cord” is formed between the electrodes with a control voltage, consisting of ionized gas (plasma) molecules. That is why gas-discharge panels operating on this principle are called “ gas-discharge"or, which is the same -" plasma” panels.

Design

The plasma panel is a matrix of gas-filled cells enclosed between two parallel glass surfaces. Neon or xenon is usually used as the gaseous medium.

The discharge in the gas flows between the transparent electrode on the front side of the screen and the address electrodes passing along its back side. The gas discharge causes ultraviolet radiation, which, in turn, initiates the visible glow of the phosphor.

In color plasma panels, each screen pixel consists of three identical microscopic cavities containing an inert gas (xenon) and having two electrodes, front and back. After a strong voltage is applied to the electrodes, the plasma will begin to move. In doing so, it emits ultraviolet light, which hits the phosphors at the bottom of each cavity.

Phosphors emit one of the primary colors: red, green or blue. The colored light then passes through the glass and enters the viewer's eye. Thus, in plasma technology, pixels work like fluorescent tubes, but creating panels from them is rather problematic.

The first difficulty is the pixel size. Sub-pixel The plasma panel has a volume of 200 µm x 200 µm x 100 µm, and several million pixels need to be laid on the panel, one by one.

Secondly, the front electrode should be as transparent as possible. For this purpose, it is used indium tin oxide because it conducts current and is transparent. Unfortunately, plasma panels can be so large, and the oxide layer so thin, that when high currents flow, there will be a voltage drop across the resistance of the conductors, which will greatly reduce and distort the signals. Therefore, it is necessary to add intermediate connecting conductors made of chromium - it conducts current much better, but, unfortunately, is opaque.

Finally, you need to choose the right phosphors. They depend on the desired color:

Green: Zn 2 SiO 4:Mn 2+ / BaAl 12 O 19:Mn 2+
Red: Y 2 O 3:Eu 3+ / Y0.65Gd 0.35 BO 3:Eu 3
Blue: BaMgAl 10 O 17:Eu 2+

These three phosphors produce light with a wavelength between 510 and 525 nm for green, 610 nm for red and 450 nm for blue.

The last problem is pixel addressing, because, as we have already seen, in order to get the desired hue, you need to change the color intensity independently for each of the three sub-pixels. On a 1280×768 pixel plasma panel, there are approximately three million sub-pixels, resulting in six million electrodes. As you understand, laying six million tracks for independent control of sub-pixels is impossible, so the tracks must be multiplexed. The front tracks are usually built in solid lines, and the back tracks are in columns. The electronics built into the plasma panel, using a matrix of tracks, selects the pixel that needs to be lit on the panel. The operation is very fast, so the user does not notice anything - like beam scanning on CRT monitors.

In LCD panels, the principle of image formation is fundamentally different - there the light source is behind the matrix, and filters are used to separate colors into RGB.

Why are plasma panels better?

Secondly, the plasma panel is extremely versatile and allows you to use it not only as a TV, but also as a personal computer display with a large screen size. To do this, all models of plasma panels, in addition to the video input (as a rule, this is a regular AV input and S-VHS input), are also equipped with a VGA input. Therefore, such a panel will be indispensable when making presentations, as well as when used as a multifunctional information board when connected to the output of a personal computer or laptop. Well, fans of home multimedia and computer games will be just delighted: just imagine how much more advantageous it will look compared to a 17″ monitor on a 42″ screen, for example, the cockpit of a space starship or a virtual battlefield with space aliens!

Third, the “picture” of a plasma panel is very similar in nature to the image in a “real” cinema. With this “cinematic” emphasis, plasma was immediately loved by “home cinema” fans and firmly established as the N1 candidate as a high-quality display medium in high-end home theaters. Moreover, the screen size of 42″ in most cases is quite enough. Obviously with a “cinema” application in mind, most plasma displays come in 16:9 aspect ratio, which has become the de-facto standard for home theater systems.

Fourth, with such a solid screen, plasma panels have extremely compact dimensions and dimensions. The thickness of the panel with a screen size of 1 meter does not exceed 9-12 cm, and the weight is only 28-30 kg. According to these parameters, today no other type of display means can compete with plasma at least some. Suffice it to say that a color kinescope with a comparable screen size has a depth of 70 cm and weighs more than 120-150 kg! Projection rear projection TVs are also not particularly slim, and front projection TVs tend to have low image brightness. The lighting parameters of plasma PDP panels are extremely high: the image brightness is over 700 cd/m 2 with a contrast ratio of at least 500:1. And what is very important, a normal image is provided in an extremely wide horizontal angle of view: 160°. That is, already today, PDPs have reached the level of the most advanced quality levels achieved by kinescopes over 100 years of their evolution. But large-screen plasma panels have been mass-produced for less than 5 years, and they are at the very beginning of their technological development.

Fifth, plasma panels are extremely reliable. According to Fujitsu, their technical resource is at least 60,000 hours (a very good kinescope has 15,000-20,000 hours), and the rejection rate does not exceed 0.2%. That is, an order of magnitude smaller than the 1.5-2% generally accepted for color CRT TVs.

At sixth, PDPs are virtually unaffected by strong magnetic and electric fields. This allows, for example, to use them in a home theater system in conjunction with speakers with unshielded magnets. This can sometimes be important, because unlike theater speakers, many “regular” HI-FI speakers come with an unshielded magnetic circuit. In a traditional TV-based home theater, using these speakers as front speakers is very difficult due to their strong influence on the TV's kinescope. And in a PDP-based AV system, as many as you like.

Seventh, due to their shallow depth and relatively small mass, plasma panels can be easily placed in any interior and even hung on the wall in a convenient place. With another type of display, such a focus is unlikely to succeed.

Other advantages of the plasma panel

• Large diagonal. It is very expensive to produce LCD matrices of large diagonals and therefore economically unprofitable. With plasma panels, everything is exactly the opposite.
• Panel does not flicker. It does not flicker, which means it does not tire the eyes, unlike conventional CRT TVs with a refresh rate of 50 Hz.
• Best Color Reproduction. Modern plasma TVs are capable of displaying up to 29 billion colors. This is rightfully considered one of the main advantages of plasma.
• Large viewing angles. The cells of the plasma panel glow by themselves, they do not need any "shutters", as in LCD panels, which regulate the amount of transmitted light. Therefore, the viewing angle of the plasma panel is almost 180 degrees in all directions.
• Response time. The response time of a plasma panel is similar to a CRT, that is, much less than that of any LCD TV.
• Brightness and Contrast. The contrast of plasma panels is much higher than that of LCD TVs. In a modern panel, it can reach 10,000:1. And the brightness of plasmas is absolutely uniform, since there is no backlight in the traditional sense.
• Compact dimensions. The average plasma panel is no thicker than 10 cm. It can be easily screwed to the wall by ordering a special bracket.

A spoon of tar

• afterglow. The afterglow effect is typical only for plasma panels. This is because regularly activated gas emits more UV light. The unevenness of the brightness level occurs when the operating time of different cells from the moment of switching on is very different from each other. Simply put, if you watch the same channel for a long time, then its sign will appear on the screen for some time after switching the channel. Panel manufacturers do their best to overcome this shortcoming by using screen servers and other more sophisticated technologies.
• Phosphor degradation. This is the same process that can be observed in conventional CRT televisions. The panel lifetime is calculated up to the loss of half the screen brightness. For the latest generation plasma, this is approximately 60,000 hours.
• Grain. Cheap non-HD plasma TVs suffer the most from this effect. Pay attention to it when choosing a budget model, and if it suddenly becomes annoying, postpone the purchase until you can purchase a model of a higher class.
• Noisiness. Most plasmas produced today have cooling fans. Keep this in mind and be sure to listen to how much noise the panel makes before buying.

Thus, the only serious drawback of plasma panels today, by and large, is only their high price. However, compared with the cost of other display devices with the same screen size, their relative price per 1 cm (or inch) of the image diagonal is not so large.

Analysis of characteristics

The principle of further narration will be as follows: we will take a typical plate of technical characteristics of a plasma panel and go through those lines that are worth paying attention to. So:

Diagonal, resolution

The diagonals of plasma panels start at 32 inches and end at 103 inches. Of this entire range, as mentioned above, 42-inch panels with a resolution of 853 × 480 pixels are the best sold in Russia so far. This resolution is called EDTV (Extended Definition Television) and means "high-definition television". Such a TV will be enough for a comfortable pastime, since in Russia there is no free high-definition television (High Definition TV - HDTV) yet. However, HDTVs tend to be more technically advanced, process the signal better, and are even capable of "pulling" it up to HDTV levels. It turns out, of course, not very much, but these attempts are valuable in themselves. In addition, you can already buy films recorded in HD DVD format in stores.

When buying an HDTV TV, pay attention to the supported signal format. The most common is 1080i, that is, 1080 interlaced lines. Interlacing is considered to be not very good, since there will be visible teeth on the edges of objects, but this disadvantage is leveled by high resolution. Support for the more advanced 1080p progressive scan format is currently found only on very expensive TVs of the latest, ninth generation. There is also an alternative 1080i format - this is 720p with a lower resolution, but with progressive scan. It will be difficult to tell the difference between the two pictures by eye, so ceteris paribus 1080i is preferable. However, a large number of TVs support both 720p and 1080i at the same time, so you should not have any problems choosing in this regard.

Let's say a few words about various image enhancement technologies. Technologically, it so happened that the quality of the panel picture to a large extent depends on various software tricks. Each manufacturer has its own, and it happens that only their competent functioning determines all the differences visible to the eye in the picture between two TVs of different brands, but of the same cost. However, it’s still not worth choosing a TV by the number of these technologies - it’s better to peer at the quality of their work, since you can admire plasmas in any normal video equipment store for as long as you like.

When choosing a diagonal, first of all, keep in mind - the larger it is, the farther from the TV you need to sit. In the case of a 42-inch panel, your favorite sofa should be at least three meters away from it. You can, of course, sit closer, but the image formation features on the panel will surely annoy you and interfere with viewing.

Aspect Ratio

All plasma TVs have panels with . A standard 4:3 TV picture will look fine on such a screen, just the unused screen area on the sides of the picture will be filled with black. Or gray if the TV allows you to change the fill color. The TV may try to stretch the image to fill the screen, but the result of this operation, as a rule, looks sad. In some plasma stores, they “broadcast” in this mode - apparently, the staff is just too lazy to look in the menu for a checkmark to turn off the scaling function. In Russia has already begun. By default, this aspect ratio is used only in HDTV.

Brightness

There are two brightness-related panel characteristics, panel brightness and overall TV brightness. The brightness of the panel cannot be assessed on the finished product, because there is always a light filter in front of it. The brightness of the TV is the apparent brightness of the screen after the light passes through the filter. The actual brightness of the TV never exceeds half the brightness of the panel. However, the specifications of the TV indicate the original brightness, which you will never see. This is the first marketing gimmick.

Another feature of the numbers indicated in the specifications is related to the method of obtaining them. In order to protect the panel, its brightness per dot is reduced in proportion to the increase in the total area of ​​illumination. That is, if you see a brightness value of 3000 cd / m2 in the characteristics, you should know that it is obtained only with a small illumination, for example, when several white letters are displayed on a black background. If we invert this picture, we will get, for example, 300 cd/m2.

Contrast

Two characteristics are also associated with this indicator: contrast in the absence of ambient light and in the presence of it. The value given in most specifications is the contrast measured in a dark room. Thus, depending on the lighting, the contrast can drop from 3000:1 to 100:1.

Interface connectors

The vast majority of plasma TVs have at least SCART, VGA, S-Video, a component video interface, as well as conventional analog audio inputs and outputs. Consider these and other connectors in more detail:

• SCART- the number of these connectors can be up to three. At one time they were considered the most advanced, until HDMI appeared. Analog video signal and stereo sound are simultaneously transmitted via SCART.
• HDMI- some might call it the evolutionary successor to SCART. Through HDMI, you can transmit an HD signal in 1080p resolution along with eight-channel audio. Due to the outstanding bandwidth and miniaturization of the connector, some camcorders and DVD players already support the HDMI interface. And Panasonic supplies with its plasmas a remote control with the HDAVI Control function, which allows you to control not only the TV, but also other equipment connected to it via HDMI.
• VGA- This is a common computer analog connector. Through it, you can connect a computer to the plasma.
• DVI-I- a digital interface for connecting the same computer. However, there is another technique that works through DVI-I.
• S-Video- most often used to connect DVD players, game consoles and, in rare cases, a computer. Provides good image quality.
• Component video interface- an interface for transmitting an analog signal, when each of its components goes through a separate cable. Thanks to this, the component signal is the highest quality of all analog signals. For sound transmission, similar RCA connectors and cables are used - each channel "runs" along its own wire.
• Composite video interface(on one RCA connector) - as opposed to component, it provides the worst quality of signal transmission. One cable is used and, as a result, loss of color and clarity of the image is possible.

Acoustic system

Don't be under the illusion that low-power speakers built into your TV can sound good. Even if the manufacturer swears to the implementation of numerous "improving" technologies, the plasma will sound at a level sufficient only for watching the news. However, some of the most honest manufacturers do not even focus on the presence of speakers - yes, they are, but nothing more. Only external and not the cheapest speaker systems will allow you to enjoy real sound.

Energy consumption

The power consumption of the Plasma TV varies depending on the picture being displayed. So don't be alarmed if you are told that a modest 42-inch panel "eats" 360 watts. The level indicated in the specification reflects the maximum value. With a completely white screen, the plasma panel will already consume 280 watts, and with a completely black screen - 160 watts.

Finally

In conclusion, I would like to give a couple of tips. The most important thing is to carefully check the panel for the presence of “broken” pixels, or rather, dots that are constantly lit in the same color. In case of detection - demand a replacement, since this is considered an unacceptable marriage, regardless of the number of such pixels. Do not let an unscrupulous seller fool you - up to five "broken" pixels are formally permissible only for LCD panels, and even then not of the highest class. And keep in mind that some TV models come with a floor stand, that is, a bedside table. This kit will be more expensive, but the stand will be in perfect harmony with the TV and provide it with good stability.

Overall rating of the material: 4.9

SIMILAR MATERIALS (BY MARKS):

Father of the video Alexander Poniatov and AMPEX

General characteristics of image output methods

There are two main methods for displaying an image: vector method and bitmap method.

vector method . With this method, the drawing tool draws only the image of the figure and its trajectory is determined by the displayed image. The image consists of graphic primitives: line segments - vectors, arcs, circles, etc. due to the complexity of constructing a beam control system that provides fast and accurate along a complex trajectory, this method has not yet found wide application.

Raster Method scans the entire image output surface and provides a drawing element that is capable of leaving a visible mark. The tool path is constant and does not depend on the displayed image, but the tool may or may not draw individual points. In the case of using the Video monitor, as a tool for drawing an image, there is a controlled beam for a black and white image and three basic beams (Red, Green, Blue) for a color image. The beam scans the screen line by line and causes the glow of the phosphor deposited on the inner surface of the screen, Fig. 29.

In this case, when the beam moves from left to right, it is on, and when it returns from right to left, it is off. Each line is divided into a certain number of dots - pixels (Picture Elements - elementary pictures), the illumination of each of which can be controlled by the device that forms the image (graphic card).

Rice. 29 - Progressive Scan

In systems with progressive or non-interleaved the beam goes along the same lines in different frames (Fig. 29), and in systems with interlaced the beam passes through the lines shifted by half the line pitch, and therefore the beam passes the entire surface of the frame in two frame scanning cycles. This makes it possible to halve the horizontal scanning frequency and, consequently, the speed of displaying image points on the screen (Fig. 30).

Rice. 30 - Interlace

Since the inertia of human vision is at a frequency of 40-60 Hz, the frame change frequency should not be lower than this value so that a person cannot notice this change, i.e. at 50Hz. To ensure a high-quality image on the screen, the beam should have as many luminous points on the screen as possible. For example: 600 lines with 800 dots each line. Therefore, the frequency of the lines will be:

50Hz x (600)=30,000Hz=30kHz

At the same time, to display each point, a frequency is required:

30kHz x 800= 24000kHz= 48MHz

And this is a high frequency for electronic circuits.

In addition, neighboring points of the output signal are not connected to each other, so the beam intensity control frequency must be further increased by 25%, and then it will be about 60 MHz.

This bandwidth must be provided by all devices of the video path: video amplifiers, signal lines of interfaces, and the graphics adapter itself. At all these stages of signal processing and transmission, high frequency creates technical difficulties. To reduce the frequency of lines, the image is interlaced in one half-frame:

even lines are highlighted in one half-frame;

odd lines - in another half-frame.

However, image quality requires an increase in the frame rate in order to eliminate image flicker, as does an increase in the size of the monitor screen on which the image itself is displayed. In this case, the higher the frequency, the lower the performance of the graphics system when building images.

Thus, there are some optimal ratios between the work of a graphic editor and an image output monitor: the graphic editor is a master device, and the monitor with its scan generators must provide the specified synchronization parameters for the beam and frame scans.

Monitor classification

Monitor- a device designed to visually display information. A modern monitor consists of a housing, a power supply, control boards and a screen. Information (video signal) for output to the monitor comes from a computer through a video card, or from another device that generates a video signal.

According to the type of information displayed, monitors are divided into:

alphanumeric [character display system - from MDA]

• displays that display only alphanumeric information;

  displays displaying pseudographic characters.

graphic to display text and graphic (including video) information.

• vector (vector-scan display) - laser light show;

  raster-scan display - used in almost every PC graphics subsystem.

By screen type:

CRT- based on a cathode ray tube (CRT);

LCD- liquid crystal monitors (English liquid crystal display, LCD);

Plasma- based on the plasma panel (plasma display panel, PDP, gas-plasma display panel);

Projector- video projector and screen placed separately or combined in one case;

OLED monitor- on OLED technology (organic light-emitting diode - organic light-emitting diode).

By type of management, there are:

Digital;

Analog.

By display dimension:

two-dimensional (2D) - one image for both eyes

three-dimensional (3D) - a separate image is formed for each eye to obtain the effect of volume.

By type of interface cable

composite;

separated;

cathode ray monitors

The most important element of such a monitor is a kinescope, also called a cathode ray tube. A CRT is an electronic vacuum device in a glass flask, in the neck of which there is an electron gun, and at the bottom there is a screen covered with a phosphor. When heated, the electron gun emits a stream of electrons that rush towards the screen at high speed. The flow of electrons (electron beam) passes through the focusing and deflecting coils, which direct it to a specific point on the screen covered with phosphor. Under the influence of electron impacts, the phosphor emits light, which is seen by the user sitting in front of the computer screen.

CRTs use three layers of phosphor: red, green And blue. To equalize the flow of electrons, the so-called shadow mask is used - a metal plate with slots or holes that separate the red, green and blue phosphor into groups of three points of each color. Image quality is determined by the type of shadow mask used; image sharpness is affected by the distance between phosphor groups (dot spacing).

On fig. 31 shows a typical cathode ray tube in section.

Rice. 31 - Color CRT in the context: 1 - electron guns; 2 - electron beams; 3 - focusing coil; 4 - deflecting coils; 5 - anode; 6 - shadow mask; 7 - phosphor; 8 – mask and phosphor grains in magnification.

The chemical used as a phosphor is characterized by an afterglow time, which reflects the duration of the glow of the phosphor after exposure to an electron beam. The persistence time and image refresh rate must match so that there is no noticeable flickering in the image (if the persistence time is very short) and there is no blurring and doubling of the edges as a result of stacking successive frames (if the persistence time is too long).

The electron beam moves very quickly, tracing the screen in lines from left to right and from top to bottom along a path called a raster. The horizontal scan period is determined by the speed at which the beam moves across the screen. In the process of scanning (moving across the screen), the beam acts on those elementary sections of the phosphor coating of the screen where the image should appear. The intensity of the beam is constantly changing, as a result of which the brightness of the glow of the corresponding sections of the screen changes. Since the glow disappears very quickly, the electron beam must run over the screen again and again, renewing it. This process is called regeneration Images.

In most monitors, the refresh rate, also called the vertical refresh rate, is approximately 85 Hz in many modes, i.e. The screen image is updated 85 times per second. Reducing the refresh rate results in flickering of the image, which is very tiring for the eyes. Therefore, the higher the refresh rate, the more comfortable the user feels.

It is very important that the refresh rate that the monitor can provide matches the rate that the video adapter is set to. If there is no such match, the image will not appear on the screen at all, and the monitor may fail. In general, video adapters provide a much higher refresh rate than most monitors support. That is why the initial refresh rate, defined for most video adapters in order to prevent damage to the monitor, is 60 Hz.

Currently, CRT-based monitors can be considered obsolete.

LCD monitors

The screens of LCD monitors (Liquid Crystal Display, liquid crystal monitors (LCD monitors)) are made of a substance that is in a liquid state, but at the same time has some properties inherent in crystalline bodies. In fact, these are liquids with anisotropy of properties (in particular, optical properties) associated with orderliness in the orientation of molecules.

Oddly enough, liquid crystals are almost ten years older than CRTs, the first description of these substances was made back in 1888. However, for a long time no one knew how to put them into practice, and they were not interesting to anyone except physicists and chemists. At the end of 1966, RCA Corporation demonstrated a prototype LCD monitor - a digital clock.

Sharp Corporation played a significant role in the development of LCD technology. She is still among the technological leaders. The world's first calculator CS10A was produced in 1964 by this corporation. In October 1975, the first compact digital watch was made using TN LCD technology. In the second half of the 70s, a transition began from eight-segment liquid crystal indicators to the production of matrices with addressing each point. So, in 1976, Sharp released a black-and-white TV with a screen diagonal of 5.5 inches, made on the basis of an LCD matrix with a resolution of 160x120 pixels.

The principle of operation of LCD monitors

The operation of LCD monitors is based on the phenomenon of light flux polarization. It is known that the so-called polaroid crystals are capable of transmitting only that component of light whose electromagnetic induction vector lies in a plane parallel to the optical plane of the polaroid. For the rest of the light output, the polaroid will be opaque. Thus, the polaroid, as it were, "sifts" the light, this effect is called the polarization of light. When liquid substances were studied, long molecules of which are sensitive to electrostatic and electromagnetic fields and are capable of polarizing light, it became possible to control the polarization. These amorphous substances, due to their similarity with crystalline substances in electro-optical properties, as well as the ability to take the shape of a vessel, were called liquid crystals.

The screen of an LCD monitor is an array of small segments (called pixels) that can be manipulated to display information. The LCD monitor has several layers, where the key role is played by two panels made of a sodium-free and very pure glass material called a substrate or substrate, which actually contain a thin layer of liquid crystals between them, fig. 32.

Rice. 32 - LCD monitor screen structure

The panels have grooves that guide the crystals, giving them a special orientation. The striae are arranged so that they are parallel on each panel but perpendicular between two panels. Longitudinal grooves are obtained by placing thin films of transparent plastic on the glass surface, which is then processed in a special way. In contact with the grooves, the molecules in liquid crystals are oriented in the same way in all cells.

Molecules of one of the varieties of liquid crystals (nematics) in the absence of voltage rotate the electric (and magnetic) field vector in a light wave by some angle in a plane perpendicular to the beam propagation axis. The application of grooves on the glass surface makes it possible to ensure the same angle of rotation of the polarization plane for all cells. The two panels are very close to each other.

The liquid crystal panel is illuminated by a light source (depending on where it is located, liquid crystal panels work by reflection or transmission of light).

The plane of polarization of the light beam rotates by 90° when passing through one panel, fig. 33.

Rice. 33 - Rotation of the plane of polarization of the light beam

When an electric field appears, liquid crystal molecules partially line up vertically along the field, the angle of rotation of the light polarization plane becomes different from 90 degrees, and light passes through liquid crystals without hindrance, Fig. 34.

Rice. 34 - The position of molecules in the presence of an electric field

The rotation of the plane of polarization of the light beam is imperceptible to the eye, so it became necessary to add two other layers to the glass panels, which are polarizing filters. These filters pass only that component of the light beam, for which the polarization axis corresponds to the specified one. Therefore, when passing through the polarizer, the light beam will be attenuated depending on the angle between its plane of polarization and the axis of the polarizer. In the absence of voltage, the cell is transparent, since the first polarizer transmits only light with the corresponding polarization vector. Thanks to liquid crystals, the light polarization vector rotates, and by the time the beam passes to the second polarizer, it has already been rotated so that it passes through the second polarizer without problems, Fig. 35a.

Rice. 35 - The passage of light without the presence of an electric field (a) and in the presence (b)

In the presence of an electric field, the rotation of the polarization vector occurs through a smaller angle, thereby the second polarizer becomes only partially transparent to radiation. If the potential difference is such that the rotation of the plane of polarization in liquid crystals does not occur at all, then the light beam will be completely absorbed by the second polarizer, and the screen, when illuminated from behind, will appear black from the front (illumination rays are completely absorbed in the screen) Fig. 35b. If you place a large number of electrodes that create different electric fields in separate places of the screen (cell), then it will be possible, with the correct control of the potentials of these electrodes, to display letters and other image elements on the screen. The electrodes are placed in transparent plastic and can be of any shape.

Technological innovations have made it possible to limit the size of the electrodes to the size of a small dot, respectively, more electrodes can be placed on the same screen area, which increases the resolution of the LCD monitor, and allows us to display even complex images in color.

To display a color image, the monitor needs to be backlit so that the light comes from the back of the LCD. This is necessary so that a good quality image can be observed even if the environment is not bright. The color is obtained by using three filters that extract three main components from the emission of a white light source. By combining the three primary colors for each point or pixel on the screen, it is possible to reproduce any color.

In the case of color, there are several possibilities: you can make several filters one after another (leads to a small fraction of transmitted radiation), you can use the property of a liquid crystal cell - when the electric field strength changes, the angle of rotation of the radiation polarization plane changes differently for light components with different lengths waves. This feature can be used to reflect (or absorb) radiation of a given wavelength (the problem is the need to accurately and quickly change the voltage). Which mechanism is used depends on the specific manufacturer. The first method is simpler, the second more efficient.

The first LCDs were very small, around 8 inches, while today they have reached 15" sizes for use in laptops, and 20" and larger LCD monitors are being produced for desktop computers. An increase in size is followed by an increase in resolution, resulting in the emergence of new problems that have been solved with the help of emerging special technologies. One of the first concerns was the need for a standard to define display quality at high resolutions. The first step towards the goal was to increase the angle of rotation of the plane of polarization of light in crystals from 90° to 270° using STN technology.

STN is short for "Super Twisted Nematic". STN technology allows to increase the torsion angle (torsion angle) of the orientation of the crystals inside the LCD display from 90° to 270°, which provides better image contrast when the monitor is enlarged.

Often STN cells are used in pairs. This design is called DSTN (Double Super Twisted Nematic), in which one two-layer DSTN cell consists of 2 STN cells, the molecules of which rotate in opposite directions during operation. Light, passing through such a structure in a "locked" state, loses most of its energy. The contrast and resolution of DSTN is quite high, so it became possible to make a color display, in which there are three LCD cells and three primary color optical filters per pixel. Color displays are not capable of working from reflected light, so a backlight is their mandatory attribute. To reduce the dimensions, the lamp is located on the side, and opposite it is a mirror.

Rice. 36 - LCD backlight

Also, STN cells are used in TSTN (Triple Super Twisted Nematic) mode, when two thin layers of polymer film are added to improve the color reproduction of color displays or to ensure good quality of monochrome monitors.

The term passive matrix comes from dividing the monitor into dots, each of which, thanks to the electrodes, can set the orientation of the plane of polarization of the beam, independently of the others, so that as a result each such element can be individually illuminated to create an image. The matrix is ​​called passive because the technology for creating LCD displays, which was described above, cannot provide a quick change of information on the screen. The image is formed line by line by successively supplying a control voltage to individual cells, making them transparent. Due to the rather large electrical capacitance of the cells, the voltage across them cannot change quickly enough, so the picture update is slow. Such a display has many disadvantages in terms of quality because the image is not displayed smoothly and judder on the screen. The low rate of change in the transparency of the crystals does not allow the correct display of moving images.

To solve some of the problems described above, special technologies are used. To improve the quality of the dynamic image, it was proposed to increase the number of control electrodes. That is, the entire matrix is ​​divided into several independent submatrices (Dual Scan DSTN - two independent fields of the image scan), each of which contains a smaller number of pixels, so their sequential control takes less time. As a result, the LC inertia time can be reduced.

Currently, the main technologies in the manufacture of LCD displays are: TN + film, IPS (SFT) and MVA. These technologies differ in the geometry of surfaces, polymer, control plate and front electrode. Of great importance are the purity and type of polymer with liquid crystal properties used in specific developments.

TN + film (Twisted Nematic + film)

TN + film is the simplest technology. The film part in the name of the technology means an additional layer used to increase the viewing angle (approximately from 90° to 150°). At present, the film prefix is ​​often omitted, calling such matrices simply TN. Unfortunately, a way to improve the contrast and response time for TN panels has not yet been found, and the response time for this type of matrix is ​​\u200b\u200bcurrently one of the best, but the contrast level is not.

The TN matrix works like this: if no voltage is applied to the pixels, the liquid crystals (and the polarized light they transmit) rotate 90° relative to each other in a horizontal plane in the space between the two plates. And since the direction of polarization of the filter on the second plate makes an angle of 90° with the direction of polarization of the filter on the first plate, light passes through it. If the red, green, and blue sub-pixels are fully illuminated, a white dot will form on the screen.

TO virtues technologies include the shortest response time among modern matrices, as well as low cost.

Flaws: Worst color reproduction, smallest viewing angles.

IPS (In-Plane Switching) or SFT (Super Fine TFT)

In-Plane Switching (Super Fine TFT) technology was developed by Hitachi and NEC. These companies use these two different names for the same technology - NEC technologies ltd. uses SFT while Hitachi uses IPS. The technology was intended to get rid of the shortcomings of TN + film. However, at first, although IPS was able to achieve an increase in viewing angle of up to 170 °, as well as high contrast and color reproduction, the response time remained at a low level.

If no voltage is applied to the IPS, the liquid crystal molecules do not rotate. The second filter is always rotated perpendicular to the first, and no light passes through it. Therefore, the display of black color is close to ideal. If the transistor fails, the “broken” pixel for the IPS panel will not be white, as for the TN matrix, but black.

When a voltage is applied, liquid crystal molecules rotate perpendicular to their initial position and transmit light.

IPS has now been superseded by various modifications of S-IPS (Super-IPS) technology, which inherits all the advantages of IPS technology with a simultaneous decrease in response time, as well as an increase in contrast.

Advantages: excellent color reproduction, wide viewing angles

Flaws A: long response time, high cost.

VA (Vertical Alignment)

Matrices MVA / PVA are considered a compromise between TN and IPS, both in terms of cost and consumer qualities. MVA (Multi-domain Vertical Alignment). This technology was developed by Fujitsu as a compromise between TN and IPS technologies. Horizontal and vertical viewing angles for MVA matrices are 160° (up to 176-178° on modern monitor models), while thanks to the use of acceleration technologies (RTC), these matrices are not far behind TN + Film in response time, but significantly exceed the characteristics of the latter color depth and fidelity.

MVA is the successor to VA technology introduced in 1996 by Fujitsu. The liquid crystals of the VA matrix, when the voltage is off, are aligned perpendicular to the second filter, that is, they do not transmit light. When voltage is applied, the crystals rotate 90° and a bright dot appears on the screen. As in IPS-matrices, pixels do not transmit light in the absence of voltage, therefore, when they fail, they are visible as black dots.

Virtues MVA technologies are deep black and lack both a helical crystal structure and a double magnetic field.

Flaws MVA versus S-IPS: Loss of detail in shadows when viewed perpendicularly, image color balance dependent on viewing angle.

The analogues of MVA are technologies:

PVA (Patterned Vertical Alignment) from Samsung.

Super PVA from Samsung.

Super MVA by CMO.

Main technical characteristics LCD monitors

Permission- horizontal and vertical dimensions expressed in pixels. Unlike CRT monitors, LCDs have one fixed resolution, the rest are achieved by interpolation;

Dot size(pixel size) - the distance between the centers of adjacent pixels. Directly related to physical resolution;

Screen aspect ratio (proportional format) - the ratio of width to height (5:4, 4:3, 16:9, etc.);

Visible Diagonal- the size of the panel itself, measured diagonally. The display area also depends on the format: a 4:3 monitor has a larger area than a 16:9 monitor with the same diagonal;

Contrast- the ratio of the brightness of the lightest and darkest points. Some monitors use an adaptive backlight level using additional lamps, the contrast figure given for them (called dynamic) does not apply to a static image;

Brightness- the amount of light emitted by the display, usually measured in candelas per square meter;

Response time- the minimum time required for a pixel to change its brightness;

Viewing angle- the angle at which the drop in contrast reaches the specified one is calculated differently for different types of matrices and by different manufacturers, and often cannot be compared.

Advantages and disadvantages of LCD monitors

To their benefits LCD can be classified as:

small size and weight in comparison with CRT;

LCD monitors, unlike CRTs, do not have visible flicker, beam focusing defects, interference from magnetic fields, problems with image geometry and clarity;

The power consumption of LCD monitors, depending on the model, settings and output image, may be significantly lower;

The power consumption of LCD monitors is 95% determined by the power of the backlights or the LCD backlight LED array.

On the other hand, LCD monitors also have some flaws, often fundamentally difficult to remove, for example:

Unlike CRTs, they can display a clear image in only one (“standard”) resolution. The rest are achieved by lossy interpolation;

Color gamut and color accuracy are lower than those of plasma panels and CRTs, respectively. On many monitors there is an unrecoverable unevenness in the transmission of brightness (bands in gradients);

Many LCD monitors have relatively low contrast and black depth. The widely used glossy coating of the matrix only affects the subjective contrast in ambient light conditions;

Due to the strict requirements for a constant thickness of the matrices, there is a problem of uniform color unevenness (backlight unevenness);

The actual image change rate also remains lower than that of CRT and plasma displays;

The dependence of the contrast on the viewing angle is still a significant disadvantage of the technology;

The maximum permissible number of defective pixels, depending on the screen size, is determined in the international standard ISO 13406-2 (in Russia - GOST R 52324-2005). The standard defines 4 quality classes for LCD monitors. The highest class - 1, does not allow the presence of defective pixels at all. The lowest, 4, allows for up to 262 defective pixels per 1 million workers.

Plasma monitors

Size has always been a major hurdle in creating widescreen monitors. Monitors larger than 24" made using CRT technology were too heavy and bulky. LCD monitors are flat and light, but screens larger than 20" were too expensive. Next generation plasma technology is ideal for large screens.

The idea of ​​a plasma panel did not come from purely scientific interest. None of the existing technologies could cope with two simple tasks: to achieve high-quality color reproduction without the inevitable loss of brightness, and to create a wide-screen TV that does not take up the entire area of ​​the room. And plasma panels (PDP), then only theoretically, could just solve such a problem. At first, experimental plasma screens were monochrome (orange) and could only meet the demand of specific consumers who needed, first of all, a large image area. Therefore, the first batch of PDPs (about a thousand pieces) was bought by the New York Stock Exchange.

The direction of plasma monitors was revived after it became completely clear that neither LCD monitors nor CRTs were able to inexpensively provide screens with large diagonals (more than twenty-one inches). Therefore, the leading manufacturers of consumer televisions and computer monitors, such as Hitachi, NEC and others, returned to PDP again.

The principle of operation of a plasma panel is a controlled cold discharge of a rarefied gas (xenon or neon) in an ionized state (cold plasma). The working element (pixel) that forms a single point of the image is a group of three subpixels responsible for the three primary colors, respectively. Each subpixel is a separate microchamber, on the walls of which there is a fluorescent substance of one of the primary colors, Fig. 37. Pixels are located at the intersection points of the transparent control chromium-copper-chromium electrodes, forming a rectangular grid.

Rice. 37 - Structure of the plasma panel

In order to "ignite" a pixel, the following occurs. Two supply and control electrodes orthogonal to each other, at the intersection point of which the desired pixel is located, are supplied with a high control alternating voltage of a rectangular shape. The gas in the cell gives up most of its valence electrons and goes into the plasma state. Ions and electrons are alternately collected at the electrodes on opposite sides of the chamber, depending on the phase of the control voltage. To "ignite" the scanning electrode, a pulse is applied, the potentials of the same name are added, the electrostatic field vector doubles its value. A discharge occurs - some of the charged ions give off energy in the form of radiation of light quanta in the ultraviolet range (depending on the gas). In turn, the fluorescent coating, being in the discharge zone, begins to emit light in the visible range, which is perceived by the observer. 97% of the ultraviolet radiation that is harmful to the eyes is absorbed by the outer glass. The brightness of the glow of the phosphor is determined by the magnitude of the control voltage.

Rice. 38 - The process of generating visible light by the cell

Main advantages. High brightness (up to 500 cd/m2) and contrast ratio (up to 400:1), along with the absence of judder, are the big advantages of such monitors (For comparison: a professional CRT monitor has a brightness of approximately 350, while a TV has a brightness of 200 to 270 cd/ m2 with a contrast ratio of 150:1 to 200:1). The high definition of the image is maintained on the entire working surface of the screen. In addition, the angle relative to the normal at which to see a normal image on plasma monitors is significantly larger than on LCD monitors. In addition, plasma panels do not create magnetic fields (which guarantees their harmlessness to health), do not suffer from vibration, like CRT monitors, and their short regeneration time allows them to be used to display video and TV signals. The absence of distortion and problems of convergence of electron beams and their focusing is inherent in all flat panel displays. It should also be noted that PDP monitors are resistant to electromagnetic fields, which allows them to be used in industrial conditions - even a powerful magnet placed next to such a display will not affect the image quality in any way. At home, you can put any speakers on the monitor without fear of colored spots on the screen.

The main disadvantages of this type of monitors is a rather high power consumption, which increases with an increase in the diagonal of the monitor and low resolution, due to the large size of the image element. In addition, the properties of the phosphor elements quickly deteriorate and the screen becomes less bright, so the life of plasma monitors in most cases is limited to 10,000 hours (this is about 5 years for office use). Due to these limitations, such monitors are currently used only for conferences, presentations, information boards, ie. where large screen sizes are required to display information. However, there is every reason to believe that the existing technological limitations will soon be overcome, and with a decrease in cost, this type of device can be successfully used as television screens or monitors for computers.

OLED technology

Operating principle. To create organic light-emitting diodes (OLED), thin-film multilayer structures consisting of layers of several polymers are used. When a positive voltage relative to the cathode is applied to the anode, the flow of electrons flows through the device from the cathode to the anode. Thus, the cathode gives electrons to the emission layer, and the anode takes electrons from the conductive layer, or in other words, the anode gives holes to the conductive layer. The emissive layer receives a negative charge, while the conductive layer receives a positive charge. Under the action of electrostatic forces, electrons and holes move towards each other and recombine when they meet. This happens closer to the emission layer, because in organic semiconductors, holes have greater mobility than electrons. During recombination, the energy of the electron decreases, which is accompanied by the release (emission) of electromagnetic radiation in the visible light region. Therefore, the layer is called the emission layer. The device does not work when a negative voltage relative to the cathode is applied to the anode. In this case, holes move towards the anode, and electrons move in the opposite direction towards the cathode, and no recombination occurs.

Rice. 39 - Scheme of a 2-layer OLED panel: 1 - cathode (-); 2 - emission layer; 3 - emitted radiation; 4 - conductive layer; 5 - anode (+)

The anode material is usually indium oxide doped with tin. It is transparent to visible light and has a high work function which promotes hole injection into the polymer layer. Metals such as aluminum and calcium are often used to fabricate the cathode, as they have a low work function that promotes electron injection into the polymer layer.

Classification according to the method of management. There are two types of OLED displays - PMOLED and AMOLED. The difference lies in the way the matrix is ​​controlled - it can be either a passive matrix (PM) or an active matrix (AM).

IN PMOLED -Displays use controllers to scan the image into rows and columns. To light a pixel, you need to turn on the corresponding row and column: at the intersection of the row and column, the pixel will emit light. You can make only one pixel glow in one cycle. Therefore, in order to make the entire display glow, it is necessary to signal all the pixels very quickly by iterating through all the rows and columns. How it's done in the old ones.

Rice. 40 - Diagram of an OLED panel with a passive matrix

PMOLED displays are cheap, but due to the need for horizontal scanning of the image, it is not possible to obtain large-sized displays with acceptable image quality. Typically, PMOLED displays do not exceed 3" (7.5 cm).

IN AMOLED -displays each pixel is controlled directly, so they can quickly reproduce the image. To control each OLED cell, transistors are used that store the information necessary to maintain the luminosity of a pixel. The control signal is applied to a specific transistor, due to which the cells are updated quickly enough. AMOLED displays can be large in size, and 40" (100 cm) displays have already been made. AMOLED displays are expensive to manufacture due to the complex pixel control scheme, unlike PMOLED displays where a simple controller is enough to control .

Rice. 41 - Diagram of an OLED active matrix panel

Classification by light-emitting material. Currently, two technologies are mainly developed that have shown the greatest efficiency. They differ in the organic materials used, these are micromolecules (sm-OLED) and polymers (PLED), the latter are divided into simple polymers, organopolymer compounds (POLED), and phosphorescent ones (PHOLED).

Schemes of color OLED displays. There are three color OLED display schemes:

scheme with separate color emitters;

WOLOD+CF scheme (white emitters + color filters);

scheme with conversion of short-wave radiation.

The simplest and most familiar option is the usual three-color model, which in OLED technology is called a model with separate emitters. Three organic materials emit light in basic colors - R, G and B. This option is the most efficient in terms of energy use, however, in practice it turned out to be quite difficult to find materials that will emit light at the desired wavelength, and even with the same brightness.

Rice. 42 - Color OLED Display Schematics

The second option uses three identical white emitters that radiate through color filters, but it loses significantly in terms of energy efficiency to the first option, since a significant part of the emitted light is lost in the filters.

The third option (CCM - Color Changing Media) uses blue emitters and specially selected luminescent materials to convert short-wavelength blue radiation into longer wavelengths - red and green. The blue emitter naturally radiates "directly". Each of the options has its own advantages and disadvantages:

The main directions of modern research and development

PHOLED (Phosphorescent OLED) - a technology that is an achievement of the Universal Display Corporation (UDC) in collaboration with Princeton University and the University of Southern California. Like all OLEDs, PHOLEDs function in the following way: an electric current is applied to organic molecules, which emit bright light. However, PHOLEDs use the principle of electrophosphorescence to convert up to 100% of electrical energy into light. For example, traditional fluorescent OLEDs convert approximately 25-30% of electrical energy into light. Due to their extremely high level of energy efficiency, even when compared to other OLEDs, PHOLEDs are being explored for potential use in large displays such as television monitors or screens for lighting needs. Potential use of PHOLED for lighting: You can cover walls with giant PHOLED displays. This would allow all rooms to be lit evenly, instead of using light bulbs that spread the light unevenly across the room. Or monitors-walls or windows - convenient for organizations or those who like to experiment with the interior. Also, the advantages of PHOLED displays include bright, saturated colors, as well as a fairly long service life.

TOLED - transparent light-emitting devices TOLED (Transparent and Top-emitting OLED) - a technology that allows you to create transparent (Transparent) displays, as well as achieve a higher level of contrast.

Rice. 43 - Example of using TOLED display

Transparent TOLED displays: the direction of light emission can be only up, only down, or both (transparent). TOLED can significantly improve contrast, which improves the readability of the display in bright sunlight.

Since TOLEDs are 70% transparent when turned off, they can be mounted directly on the windshield of a car, on storefronts or for installation in a virtual reality helmet. Also, the transparency of TOLEDs allows them to be used with metal, foil, silicon crystal, and other opaque substrates for forward-facing displays (may be used in future dynamic credit cards). Screen transparency is achieved by using transparent organic elements and materials for the manufacture of electrodes.

By using a low-reflection absorber for the TOLED display substrate, the contrast ratio can be an order of magnitude superior to LCDs (mobile phones and cockpits of military fighter aircraft). TOLED technology can also be used to produce multi-layer devices (eg SOLED) and hybrid arrays (Bi-directional TOLEDs make it possible to double the display area for the same screen size - for devices where the desired amount of displayed information is wider than the existing one).

FOLED (Flexible OLED) - the main feature is the flexibility of the OLED display. A plastic or flexible metal plate is used as a substrate on one side, and OLED cells in a sealed thin protective film on the other. The advantages of FOLED: ultra-thin display, ultra-low weight, strength, durability and flexibility, which allows OLED panels to be used in the most unexpected places.

Stacked OLED - screen technology from UDC (stacked OLED). SOLEDs use the following architecture: the image of sub-pixels is stacked (red, blue and green elements in each pixel) vertically instead of side by side, as is the case in an LCD or cathode ray tube. In SOLED, each subpixel element can be controlled independently. The color of a pixel can be adjusted by changing the current flowing through the three colored elements (non-color displays use pulse width modulation). Brightness is controlled by changing the current strength. Advantages of SOLED: high density of filling the display with organic cells, whereby a good resolution is achieved, which means a high-quality picture. .(SOLED displays have 3 times better picture quality than LCD and CRT.

Advantages and disadvantages OLED

Advantages:

Advantages compared to plasma displays:

smaller dimensions and weight;

lower power consumption at the same brightness;

the ability to create flexible screens.

Advantages compared to liquid crystal displays:

smaller dimensions and weight;

no need for lighting;

the absence of such a parameter as the viewing angle - the image is visible without loss of quality from any angle.

instant response (an order of magnitude higher than that of LCD) - in fact, the complete absence of inertia;

better color reproduction (high contrast);

the ability to create flexible screens;

large operating temperature range (from -40 to +70C).

Brightness. OLED displays range from a few cd/m2 (for night operation) to very high luminances of over 100,000 cd/m2 and can be dimmed over a very wide dynamic range. Since the life of a display is inversely proportional to its brightness, it is recommended that instruments operate at more moderate brightness levels up to 1000 cd/m2. When the LCD display is illuminated with a bright beam of light, glare appears, and the picture on the OLED screen will remain bright and saturated in any light level (even when the display is directly exposed to sunlight).

Contrast. Here OLED is also the leader. OLED displays have a contrast ratio of 1000000:1 (LCD contrast is about 5000:1, CRT is about 2000:1)

viewing angles. OLED technology allows you to view the display from any side and from any angle, and without loss of image quality.

Energy consumption. Less power consumption at the same brightness.

Flaws:

short service life of phosphors of some colors (about 2-3 years);

high cost and undeveloped technology for creating large matrices;

The main problem for OLED is that the continuous operation time should not exceed 15,000 hours. The problem that currently prevents widespread adoption of this technology is that the "red" OLED and "green" OLED can continuously operate for tens of thousands of hours longer than the "blue" OLED. This visually distorts the image, and the quality display time is unacceptable for a commercially viable device. However, this can be considered temporary difficulties in the development of a new technology, since new and more durable phosphors are being developed.

The plasma panel is a matrix of gas-filled cells enclosed between two parallel glass plates, inside of which there are transparent electrodes that form scanning, illumination and addressing buses, respectively. The discharge in the gas flows between the discharge electrodes (scanning and illumination) on the front side of the screen and the addressing electrode on the back side.

Design features:

· the sub-pixel of the plasma panel has the following dimensions: 200 µm × 200 µm × 100 µm;

· The front electrode is made of indium tin oxide, as it conducts current and is as transparent as possible.

· when high currents flow through a rather large plasma screen, due to the resistance of the conductors, a significant voltage drop occurs, leading to signal distortions, and therefore intermediate chromium conductors are added, despite its opacity;

· To create a plasma, cells are usually filled with gas - neon or xenon (He and / or Ar are used less often, or, more often, their mix-mixes).

Phosphors in plasma panel pixels have the following composition:

· Green: Zn 2 SiO 4: Mn 2+ / BaAl 12 O 19: Mn 2+ ; + / YBO 3: Tb / (Y, Gd) BO 3: Eu

Red: Y 2 O 3: Eu 3+ / Y 0.65 Gd 0.35 BO 3: Eu 3+

Blue: BaMgAl 10 O 17: Eu 2+

The existing problem in addressing millions of pixels is solved by arranging a pair of front tracks as rows (scan and backlight buses) and each back track as columns (address bus). The internal electronics of plasma screens automatically select the correct pixels. This operation is faster than beam scanning on CRT monitors. In the latest PDP models, screen refresh occurs at frequencies of 400-600 Hz, which prevents the human eye from noticing screen flicker.

The principle of operation of the monitor is based on plasma technology: the effect of the glow of an inert gas under the influence of electricity is used (approximately the same as neon lamps work).

The operation of the plasma panel consists of three stages:

1. Initialization, during which the position of the charges of the medium is ordered and it is prepared for the next stage (addressing). At the same time, there is no voltage on the addressing electrode, and an initialization pulse having a stepped form is applied to the scanning electrode relative to the backlight electrode. At the first stage of this pulse, the ordering of the arrangement of the ionic gaseous medium occurs, at the second stage, the discharge in the gas, and at the third stage, the ordering is completed.

2. Addressing, during which the pixel is prepared for highlighting. A positive pulse (+75 V) is applied to the address bus, and a negative pulse (-75 V) is applied to the scan bus. On the backlight bus, the voltage is set to +150 V.

3. Illumination, during which a positive pulse is applied to the scanning bus, and a negative pulse equal to 190 V is applied to the illumination bus. The sum of the ion potentials on each bus and additional pulses leads to an excess of the threshold potential and a discharge in a gaseous medium. After the discharge, the ions are redistributed at the scan and illumination buses. The change in the polarity of the pulses leads to a repeated discharge in the plasma. Thus, by changing the polarity of the pulses, a multiple discharge of the cell is ensured.

One cycle "initialization - addressing - highlighting" forms the formation of one image subfield. By adding several subfields, it is possible to provide an image of a given brightness and contrast. In the standard version, each frame of the plasma panel is formed by adding eight subfields.

Figure 1. Construction in cells

Thus, when a high-frequency voltage is applied to the electrodes, gas ionization or plasma formation occurs. A capacitive high-frequency discharge occurs in the plasma, which leads to ultraviolet radiation, which causes the phosphor to glow: red, green or blue. This glow, passing through the front glass plate, enters the eye of the viewer.

The operation of plasma monitors is very similar to the operation of neon lamps, which are made in the form of a tube filled with low pressure inert gas. A pair of electrodes is placed inside the tube, between which an electric discharge is ignited and a glow occurs. Plasma screens are created by filling the space between two glass surfaces with an inert gas such as argon or neon. Then, small transparent electrodes are placed on the glass surface, to which a high-frequency voltage is applied. Under the action of this voltage, an electric discharge occurs in the gas region adjacent to the electrode. The gas discharge plasma emits light in the ultraviolet range, which causes the phosphor particles to glow in the range visible to humans.

In fact, every pixel on the screen works like a regular fluorescent lamp (in other words, a fluorescent lamp). The basic principle of operation of a plasma panel is a controlled cold discharge of a rarefied gas (xenon or neon) in an ionized state (cold plasma). The working element (pixel) that forms a single point of the image is a group of three subpixels responsible for the three primary colors, respectively. Each subpixel is a separate microchamber, on the walls of which there is a fluorescent substance of one of the primary colors. The pixels are located at the intersection points of the transparent control chromium-copper-chromium electrodes, forming a rectangular grid.

Figure 2. Construction in a cell

In order to "light up" a pixel, something like this happens. A high control alternating voltage of a rectangular shape is applied to the supply and control electrodes, orthogonal to each other, at the point of intersection of which the desired pixel is located. The gas in the cell gives up most of its valence electrons and goes into the plasma state. Ions and electrons are alternately collected at the electrodes, on opposite sides of the chamber, depending on the phase of the control voltage. For "ignition" a pulse is applied to the scanning electrode, the potentials of the same name are added, and the electrostatic field vector doubles its value. A discharge occurs - some of the charged ions give off energy in the form of radiation of light quanta in the ultraviolet range (depending on the gas). In turn, the fluorescent coating, being in the discharge zone, begins to emit light in the visible range, which is perceived by the observer. 97% of the ultraviolet radiation that is harmful to the eyes is absorbed by the outer glass. The brightness of the glow of the phosphor is determined by the magnitude of the control voltage.

Figure 3. Cell arrangement of a color AC gas discharge panel

High brightness (up to 650 cd/m2) and contrast ratio (up to 3000:

1) along with the lack of jitter are the big advantages of such monitors (For comparison: a professional CRT monitor has a brightness of approximately 350 cd / m2, and a TV has from 200 to 270 cd / m2 with a contrast ratio of 150: 1 to 200:

1). The high definition of the image is maintained on the entire working surface of the screen. In addition, the angle relative to the normal at which to see a normal image on plasma monitors is significantly larger than on LCD monitors. In addition, plasma panels do not create magnetic fields (which guarantees their harmlessness to health), do not suffer from vibration, like CRT monitors, and their short regeneration time allows them to be used to display video and TV signals. The absence of distortion and problems of convergence of electron beams and their focusing is inherent in all flat panel displays. It should also be noted that PDP monitors are resistant to electromagnetic fields, which allows them to be used in industrial conditions - even a powerful magnet placed next to such a display will not affect the image quality in any way. At home, you can put any speakers on the monitor without fear of colored spots on the screen.

The main disadvantages of this type of monitors are rather high power consumption, which increases with the increase in the diagonal of the monitor and low resolution, due to the large size of the image element. In addition, the properties of the phosphor elements deteriorate rapidly, and the screen becomes less bright. Therefore, plasma monitors have a lifespan of 10,000 hours (about 5 years for office use). Due to these limitations, such monitors are used so far only for conferences, presentations, information boards, that is, where large screen sizes are required to display information.

In a cathode ray tube monitor, image points are displayed using a beam (electron beam) that causes the phosphor-coated screen surface to glow. The beam goes around the screen line by line, from left to right and from top to bottom. A complete cycle of displaying a picture is called a "frame". The faster the monitor displays and redraws frames, the more stable the picture seems, the flicker is less noticeable and our eyes get tired less.

CRT monitor device. 1 - Electron guns. 2 - Electron beams. 3 - Focusing coil. 4 - Deflecting coils. 5 - Anode. 6 - Mask, due to which the red beam hits the red phosphor, etc. 7 - Red, green and blue grains of the phosphor. 8 - Mask and phosphor grains (enlarged).

LCD

Liquid crystal displays were developed in 1963 at RCA's David Sarnoff Research Center in Princeton, New Jersey.

Device

Structurally, the display consists of an LCD matrix (a glass plate, between the layers of which liquid crystals are located), light sources for illumination, a contact harness and a frame (case), more often plastic, with a metal frame of rigidity. Each pixel of the LCD matrix consists of a layer of molecules between two transparent electrodes, and two polarizing filters, the polarization planes of which are (usually) perpendicular. If there were no liquid crystals, then the light transmitted by the first filter would be almost completely blocked by the second filter. The surface of the electrodes in contact with liquid crystals is specially treated for the initial orientation of the molecules in one direction. In the TN matrix, these directions are mutually perpendicular, so the molecules line up in a helical structure in the absence of stress. This structure refracts light in such a way that before the second filter its polarization plane rotates and the light passes through it without loss. Apart from the absorption of half of the unpolarized light by the first filter, the cell can be considered transparent. If a voltage is applied to the electrodes, then the molecules tend to line up in the direction of the electric field, which distorts the helical structure. In this case, the elastic forces counteract this, and when the voltage is turned off, the molecules return to their original position. At a sufficient field strength, almost all molecules become parallel, which leads to the opacity of the structure. By varying the voltage, you can control the degree of transparency. If a constant voltage is applied for a long time, the liquid crystal structure may degrade due to ion migration. To solve this problem, an alternating current is applied or a change in the polarity of the field with each addressing of the cell (since the change in transparency occurs when the current is turned on, regardless of its polarity). In the entire matrix, it is possible to control each of the cells individually, but as their number increases, this becomes difficult, as the number of required electrodes increases. Therefore, addressing by rows and columns is used almost everywhere. The light passing through the cells can be natural - reflected from the substrate (in LCD displays without backlight). But more often an artificial light source is used, in addition to independence from external lighting, this also stabilizes the properties of the resulting image. Thus, a full-fledged LCD monitor consists of high-precision electronics that processes the input video signal, an LCD matrix, a backlight module, a power supply, and a housing with controls. It is the combination of these components that determines the properties of the monitor as a whole, although some characteristics are more important than others.

Backlight

By themselves, liquid crystals do not glow. In order for the image on the liquid crystal display to be visible, a light source is needed. The source can be external (for example, the Sun) or built-in (backlight). Typically, built-in backlight lamps are located behind the liquid crystal layer and shine through it (although there are also side lights, for example, in watches).

• External lighting

The monochrome displays of wristwatches and mobile phones use ambient light most of the time (from the Sun, room lights, etc.). Typically, behind the liquid crystal pixel layer is a specular or matte reflective layer. For use in the dark, such displays are equipped with side illumination. There are also transflective displays, in which the reflective (mirror) layer is translucent, and the backlights are located behind it.

• Incandescent lighting
In the past, some monochrome LCD wristwatches used a subminiature incandescent light bulb. But due to the high energy consumption, incandescent lamps are disadvantageous. In addition, they are not suitable for use, for example, in televisions, as they generate a lot of heat (overheating is harmful to liquid crystals) and often burn out.
• Illumination by gas-discharge ("plasma") lamps
During the first decade of the 21st century, the vast majority of LCD displays were backlit by one or more gas discharge lamps (most often cold cathode - CCFL). In these lamps, the light source is a plasma that occurs when an electrical discharge through a gas. Such displays should not be confused with plasma displays, in which each pixel itself glows and is a miniature gas discharge lamp.
• Light-emitting diode (LED) backlight
At the border of the first and second decades of the 21st century, LCD displays that are backlit by one or a small number of light-emitting diodes (LEDs) have become widespread. These LCDs (commonly referred to as LEDs in the trade) should not be confused with true LED displays, in which each pixel glows on its own and is a miniature LED.

Advantages and disadvantages

Currently, LCD monitors are the main, rapidly developing direction in monitor technology. Their advantages include: small size and weight in comparison with CRT. LCD monitors, unlike CRTs, do not have visible flicker, beam focusing defects, interference from magnetic fields, problems with image geometry and clarity. The power consumption of LCD monitors, depending on the model, settings and displayed image, can either coincide with the consumption of CRT and plasma screens of comparable sizes, or be significantly - up to five times - lower. The power consumption of LCD monitors is 95% determined by the power of the backlight lamps or the LED backlight matrix (English backlight - back light) of the LCD matrix. In many monitors in 2007, to adjust the brightness of the screen glow by the user, pulse-width modulation of the backlight lamps with a frequency of 150 to 400 or more hertz is used. On the other hand, LCD monitors also have some drawbacks, often fundamentally difficult to eliminate, for example:

• Unlike CRTs, they can display a clear image in only one (“standard”) resolution. The rest are achieved by interpolation with loss of clarity. Moreover, too low resolutions (eg 320*200) cannot be displayed at all on many monitors.
• Many LCD monitors have relatively low contrast and black depth. Increasing the actual contrast is often associated with simply increasing the brightness of the backlight, up to uncomfortable values. The widely used glossy coating of the matrix affects only the subjective contrast in ambient light conditions.
• Due to the strict requirements for a constant thickness of the matrices, there is a problem of uniform color unevenness (backlight unevenness) - on some monitors there is an unremovable brightness unevenness (stripes in gradients) associated with the use of blocks of linear mercury lamps.
• The actual image change rate also remains lower than that of CRT and plasma displays. Overdrive technology solves the problem of speed only partially.
• The dependence of the contrast on the viewing angle is still a significant disadvantage of the technology.
• Mass-produced LCD monitors are not well protected from damage. The matrix unprotected by glass is especially sensitive. With strong pressure, irreversible degradation is possible. There is also the problem of defective pixels. The maximum permissible number of defective pixels, depending on the screen size, is determined in the international standard ISO 13406-2 (in Russia - GOST R 52324-2005). The standard defines 4 quality classes for LCD monitors. The highest class - 1, does not allow the presence of defective pixels at all. The lowest, 4, allows for up to 262 defective pixels per 1 million workers.
• LCD monitor pixels degrade, although the rate of degradation is the slowest of all display technologies, with the exception of laser displays, which are not.

OLED (organic light-emitting diode) displays are often considered a promising technology that can replace LCD monitors, but it has met with difficulties in mass production, especially for large diagonal matrices.

Plasma monitors

The plasma panel is a matrix of gas-filled cells enclosed between two parallel glass plates, inside of which there are transparent electrodes that form scanning, illumination and addressing buses. The discharge in the gas flows between the discharge electrodes (scanning and illumination) on the front side of the screen and the addressing electrode on the back side.

OLED monitors

An organic light-emitting diode (OLED) is a semiconductor device made from organic compounds that efficiently emits light when an electric current is passed through it. Based on it, OLED monitors are made. It is assumed that the production of such displays will be much cheaper than the production of liquid crystal displays.

Operating principle

To create organic light-emitting diodes (OLED), thin-film multilayer structures consisting of layers of several polymers are used. When a positive voltage relative to the cathode is applied to the anode, the flow of electrons flows through the device from the cathode to the anode. Thus, the cathode gives electrons to the emission layer, and the anode takes electrons from the conductive layer, or in other words, the anode gives holes to the conductive layer. The emissive layer receives a negative charge, while the conductive layer receives a positive charge. Under the action of electrostatic forces, electrons and holes move towards each other and recombine when they meet. This happens closer to the emission layer, because in organic semiconductors, holes have greater mobility than electrons. During recombination, a decrease in the energy of the electron occurs, which is accompanied by the emission (emission) of electromagnetic radiation in the visible light region. Therefore, the layer is called the emission layer. The device does not work when a negative voltage relative to the cathode is applied to the anode. In this case, holes move towards the anode, and electrons move in the opposite direction towards the cathode, and no recombination occurs. The anode material is usually indium oxide doped with tin. It is transparent to visible light and has a high work function which promotes hole injection into the polymer layer. Metals such as aluminum and calcium are often used to fabricate the cathode, as they have a low work function that promotes electron injection into the polymer layer.

Advantages

Compared to plasma displays

• smaller dimensions and weight
• lower power consumption at the same brightness
• the ability to show a static image for a long time without screen burn-in

Compared to liquid crystal displays

• smaller dimensions and weight
• no need for lighting
• the absence of such a parameter as viewing angle - the image is visible without loss of quality from any angle
• instant response (an order of magnitude higher than LCD) - in fact, the complete absence of inertia
• better color reproduction (high contrast)
• the ability to create flexible screens
• large operating temperature range (?40 to +70 °C)

Brightness. OLED displays range from a few cd/m2 (for night operation) to very high luminances of over 100,000 cd/m2 and can be dimmed over a very wide dynamic range. Since the life of a display is inversely proportional to its brightness, it is recommended that instruments operate at more moderate brightness levels up to 1000 cd/m2.

Contrast. Here OLED is also the leader. OLED displays have a contrast ratio of 1,000,000:1 (LCD contrast up to 2000:1, CRT up to 5000:1)

viewing angles. OLED technology allows you to view the display from any side and from any angle, and without loss of image quality. However, modern LCD displays (with the exception of those based on TN + Film matrices) also retain acceptable picture quality at large viewing angles.

Energy consumption.

Flaws

The main problem for OLED is that the continuous operation time should be more than 15 thousand hours. One problem that currently prevents widespread adoption of this technology is that "red" OLED and "green" OLED can continuously operate tens of thousands of hours longer than "blue" OLED. This visually distorts the image, and the quality display time is unacceptable for a commercially viable device. Although today the "blue" OLED still reached the mark of 17.5 thousand hours (about 2 years) of continuous operation.

At the same time, for the displays of phones, cameras, tablets and other small devices, an average of about 5 thousand hours of continuous operation is sufficient, due to the rapid rate of obsolescence of the equipment and its irrelevance after several subsequent years. Therefore, OLED is successfully used in them today.

This can be considered temporary difficulties in the development of a new technology, since new durable phosphors are being developed. Matrix production capacities are also growing. The need for the benefits demonstrated by organic displays is growing every year. This fact allows us to conclude that in the near future displays produced using OLED technologies will most likely become dominant in the consumer electronics market.

Projection monitors

We called a projection monitor a system consisting of a projector and a projection surface.

Projector

A projector is a lighting device that redistributes the light of a lamp with a concentration of light flux on a small surface or in a small volume. Projectors are mainly optical-mechanical or optical-digital devices that allow using a light source to project images of objects onto a surface located outside the device - a screen.

Paired with a computer, it is a multimedia projector that is used (the term “Digital Projector” is also used). A real-time video signal (analogue or digital) is fed to the input of the device. The device projects an image onto the screen. It is possible that there is an audio channel.

Speaking of projectors, it is worth mentioning the so-called pico projector. This is a small, pocket size projector. Often made in the form factor of a cell phone and has a similar size. The term "pico projector" can also mean a miniature projector built into a camera, mobile phone, PDA, and other mobile devices.

Existing pocket projectors allow you to get projections up to 100 inches diagonally, with a brightness of up to 40 lumens. Mini projectors made as stand-alone devices often have a threaded hole for a standard tripod and almost always have built-in card readers or flash memory, which allows you to work without a signal source. Pico projectors use LEDs to reduce power consumption.

All about 3D

Only modern technologies are able to form on the cinema screen,TV or computer monitor three-dimensional picture.We'll show you how these technologies work.

A futuristic helicopter flies low over the heads of the audience, robotic marines clad in exo-armor sweep everything in their path, a hefty space shuttle shakes the air with the roar of engines - so close and frighteningly real that you involuntarily press your head into your shoulders. The recently released "Avatar" by James Cameron or a three-dimensional computer game make the viewer sitting in a chair in front of the screen feel like a participant in a fantastic action... Very soon, alien monsters will walk in every home where there is a modern home theater. But how is a flat screen capable of displaying a three-dimensional picture?

Man in 3D space

We see the same object with the left and right eyes at different angles, thus forming two images - a stereo pair. The brain combines both pictures into one, which is interpreted by consciousness as three-dimensional. Differences in perspective allow the brain to determine the size of an object and its distance. Based on all this information, a person receives a spatial representation with the correct proportions.

How a three-dimensional image appears

In order for the picture on the screen to appear three-dimensional, each eye of the viewer, as in life, must see a slightly different image, from which the brain will put together a single three-dimensional picture.

The first 3D films created with this principle in mind appeared on cinema screens as early as the 1950s. Since the rising popularity of television was already a serious competitor to the film industry, movie businessmen wanted to get people off the sofas and head to the cinema, enticing them with visual effects that no TV could provide at that time: color image, wide screen, multi-channel sound and , of course, three-dimensionality. The volume effect was created in several different ways.

Anaglyph method(anaglyph is Greek for “embossed”). In the early stages of 3D cinema, only black-and-white 3D films were released. In each appropriately equipped cinema, two film projectors were used to show them. One projected the film through a red filter, the other displayed slightly horizontally shifted film frames, passing them through a green filter. Visitors put on light cardboard glasses, in which, instead of glasses, pieces of red and green transparent film were installed, so that each eye saw only the necessary part of the image, and the audience perceived the “three-dimensional” picture. However, both film projectors must be directed strictly at the screen and work absolutely synchronously. Otherwise, a split image is inevitable and, as a result, headaches instead of viewing pleasure for the audience.

These glasses are also well suited for modern color 3D films, in particular those recorded using the Dolby 3D method. In this case, one projector with light filters installed in front of the lens is sufficient. Each of the filters transmits red and blue light to the left and right eyes. One image has a bluish tint, the other has a reddish tint. Light filters in the glasses pass only the appropriate frames intended for a particular eye. However, this technology allows you to achieve only a slight 3D effect, with a shallow depth.

Shutter method. Ideal for viewing color films. Unlike anaglyph, this method involves the projector alternately displaying images intended for the left and right eyes. Due to the fact that the alternation of images is carried out at a high frequency - from 30 to 100 times per second - the brain builds a coherent spatial picture and the viewer sees a solid three-dimensional image on the screen. This method was previously called NuVision, but is now more commonly referred to as XpanD.

To view 3D movies using this method, shutter glasses are used, in which two optical shutters are installed instead of glasses or filters. These small light-transmitting LCD matrices are capable of changing transparency on command from the controller - either dimming or brightening, depending on which eye the image needs to be applied to at the moment.

The shutter method is used not only in cinemas: it is also used in televisions and computer monitors. In the cinema, commands are given using an IR transmitter. Some 1990s PC shutter glasses were connected to the computer with a cable (modern models are wireless).

The disadvantage of this method is that shutter glasses are a complex electronic device that consumes electricity. Consequently, they have a rather high (especially in comparison with cardboard glasses) cost and significant weight.

polarization method. In the field of cinema, this solution is called RealD. Its essence is that the projector alternately demonstrates film frames in which light waves have different directions of polarization of the light flux. The special glasses required for viewing are equipped with filters that allow only light waves that are polarized in a certain way to pass through. So both eyes receive images with different information, on the basis of which the brain forms a three-dimensional picture.

Polarized glasses are somewhat heavier than cardboard glasses, but because they work without a power source, they weigh and cost significantly less than shutter glasses. However, along with the polarizing filters that are installed on movie projectors and glasses, this method requires an expensive screen with a special coating to display 3D films.

At the moment, preference is not finally given to any of these methods. However, it should be noted that with two projectors (by the anaglyph method) fewer and fewer cinemas are working.

How 3D movies are made

The use of complex techniques is required already at the shooting stage, and not just during the viewing of 3D movies. To create the illusion of three-dimensionality, each scene must be filmed simultaneously with two cameras, from different angles. Like the human eye, both cameras are placed close to each other, at the same height.

3D technologies for home use

To watch 3D movies on DVD, simple cardboard glasses, a legacy of the distant 50s, are still used. This explains the modest result - poor color reproduction and insufficient image depth.

However, even modern 3D technologies are tied to special glasses, and this state of affairs, apparently, will not change soon. Although Philips introduced a prototype 42-inch LCD 3D TV that does not require the use of glasses in 2008, the technology will reach its market maturity in at least 3-4 years.

But the release of 3D-TVs, working in tandem with glasses, at the international exhibition IFA 2009 was announced by several manufacturers at once. For example, Panasonic intends to release 3D TV models by mid-2010, just like Sony and Loewe, relying on the shutter method. JVC, Philips and Toshiba are also aiming for the 3D podium, but they prefer the polarization method. LG and Samsung are developing their devices based on both technologies.

Content for 3D

Blu-ray discs are the main source of 3D video content. The content is transferred to the image source via the HDMI interface. To do this, the TV and player must support the appropriate technologies, as well as the recently adopted HDMI 1.4 standard - only it provides simultaneous transmission of two 1080p data streams. So far, devices with HDMI 1.4 support can be counted on the fingers.

3D technologies on PC

Initially, viewing a three-dimensional image on a computer was available only with the help of glasses or special virtual reality helmets. Both were equipped with two color LCD displays - for each of the eyes. The quality of the resulting image when using this technology depended on the quality of the LCD screens used.

However, these devices had a number of shortcomings that scared away most buyers. Forte's cyber helmet, which appeared in the mid-90s, was bulky, ineffective, and resembled a medieval torture device. A modest resolution of 640x480 pixels was clearly not enough for computer programs and games. And although later more advanced glasses were released, for example, the Sony LDI-D 100 model, but even they were quite heavy and caused severe discomfort.

Having withstood almost a ten-year pause, technologies for forming a stereo image on a monitor screen have reached a new stage in their development. It's good news that at least one of the two major graphics adapter manufacturers, NVIDIA, has come up with something innovative. 3D Vision complex worth about 6 thousand rubles. includes shutter glasses and IR transmitter. However, to create a spatial image with these glasses, the appropriate hardware is required: the PC must be equipped with a powerful NVIDIA video card. And in order for the pseudo-three-dimensional picture not to flicker, a monitor with a resolution of 1280x1024 pixels must provide a screen refresh rate of at least 120 Hz (60 Hz for each eye). ASUS G51J 3D became the first laptop equipped with this technology.

So-called 3D profiles for more than 350 games are also currently available, which can be downloaded from the NVIDIA website (www.nvidia.ru). These include both modern action games, such as Borderlands, and previously released ones.

Continuing the theme of computer games, an alternative to shutter 3D is the polarization method. To implement it, you need a monitor with a polarizing screen, for example Hyundai W220S. 3D image becomes available with any powerful ATI or NVIDIA graphics card. However, this reduces the resolution from 1680x1050 to 1680x525 pixels, since frames are interlaced. Which games support the polarization method can be found on the Internet at: www.ddd.com.

3D camera

It is already possible to take 3D photographs today: the Fujifilm Finepix Real 3D W1 camera, with the help of two lenses and two sensors, is capable of capturing photos and even short videos with a three-dimensional spatial effect. As an accessory for the camera, a digital photo frame is offered that shows photos in 3D. Anyone who wants to print their 3D prints can go to Fuji's online photo service. The cost of one print is about 5 euros, and the delivery time for an order from the UK, where the photos are printed, is almost two weeks.

3D scanner

3D scanners are able to scan, at least for now, small objects and save their "volumetric" images as files on the hard drive. In this case, the shooting of the object, as a rule, is carried out by two cameras. Depending on its size, the subject either rotates on a special platform, or the cameras move around it. The price and date of the appearance of 3D scanners on the mass market have not yet been determined.